Variable volume reservoir



Feb. 10,1970 MC I E I 3,494,509

VARIABLE VOLUME RESERVOIR Filed Jun'e 15, 1966 4 Sheets-Sheet 1 3 :0 2.2o l8fi CARBURATOR Q I 26 I 48 3o I 'ICONTROLSI 36 I 39 INVENTOR.

33 JOHN S. MGU/RE TO PUMP T0 TANK BY A TTORNE Y3 J14 Sheets-Sheet 2 vFiled Jun; 13, 1966 INVENTOR. JOHN S. MGU/RE ATTORNEYS -Feb.1 0,.197o V5, m; 3,494509 I I VARIABLE VQLUMEURESEIIVOIR 4 Sheetls-Sheet-fi Filed Jde is, 1966 H a m 1% I m m w m m .1...

m m M we I INVENTOR. JOHN S. MGUIRE nrro/eusvs United States Patent3,494,509 VARIABLE VOLUME RESERVOIR John S. McGuire, P.O. Box 157,Ozark, Mo. 65721 Filed June 13, 1966, Ser. No. 557,170 Int. Cl. B65d89/04, 35/28 U.S. Cl. 222107 2 Claims ABSTRACT OF THE DISCLOSURE Acollapsible or variable volume reservoir or tank having first and secondpanels or walls disposed in spaced relation and interconnected by aflexible wall to form an enclosure of variable volume. The flexible wallis formed of a flexible synthetic resin material having controlledrandomly orientated molecular structure with said flexible wall being ina bellows like form to permit the space between the panels to vary andchange the volume whereby it varies in a corresponding manner to thequantity of fluid within the reservoir. The method of making a variablevolume reservoir includes the heating and expanding portions of thehollow member to obtain molecular orientation in the material thereof.

This invention relates to material handling systems and moreparticularly, to a pressure system for moving flowable materialincluding a collapsible or variable volume reservoir or tank and themethod of forming said reservoir.

It is desirable in various situations to move flowable material in acompletely closed system wherein the material is free from contaminationby moisture, dust and the like and wherein oxidation is inhibited inthat air is prevented from contactng the material. This is particularlyapplicable to fuel supply systems such as in various types of vehicles,for instance, automobiles, trucks and aircraft, where contamination ofthe fuel adversely affects vehicular performance and further, wherefumes from the fuel create hazardous conditions. Although some systemsare partial- 1y closed, the depletion of material within the systemresults in the movement of air into the system, particularly in thematerial reservoir. Contamination, leakage and exposure to air may alsooccur at various valves and pumps within the normal prior art systems.

Heretofore, variable volume tanks have been developed in an effort toreduce the formation of flammable gasses in the tank with said tankcollapsing in a corresponding manner to the removal of fuel from saidtank. These tanks, however, have not become commercially acceptedprimarily as a result of their inability to withstand the pressures,temperatures and the stresses of repeated flexing which are encounteredin the environment where the utilization of such structures isdesirable.

The principal objects of this invention are: to alleviate theaforementioned difficulties in the art by providing a new and improvedvariable volume reservoir, container or tank capable of withstanding thepressures, temperatures and repeated flexing to which a reservoir ofthis nature would be subjected in a multitude of environments; toprovide such a reservoir formed by a new and improved method wherein themolecular structure of the reservoir is formed in a controlled randomorientation, or in other Words, is comprised of oriented molecularchains disposed along randomly directed planes providing a structure ofconsiderable strength; to provide such a reservoir having sufficientstrength to impart or transfer the pressure required to move theflowable material contained in said reservoir such that additionalpumping means or valves within the material movement system are notrequired, thereby eliminating numerous sources of leakage andcontaminations; to provide a new and novel method of forming such avariable volume reservoir wherein the entire structure is strengthenedby controlled random molecular orientation which effects molecularalignment without creating the weaknesses of single plane molecularorientation which tends to form cleavage planes in the structures; toprovide a new and improved system for the handling or moving of flowablematerial wherein the storage container transmits pressure to thematerial for effecting the moving of the material; to provide such asystem which may be maintained throughout its operation in asubstantially closed condition even though the material in said systemis being depleted or utilized; to provide a fuel handling system havinga variable volume storage reservoir wherein the volume of the reservoirvaries in a corresponding manner to the depletion of fuel within saidreservoir; to provide such a fuel system wherein depletion of the fueldecreases the volume of the fuel reservoir such that the employment ofsuch reservoir on a vehicle may utilize the decreased volume to raisethe reservoir relative to the road surface, thereby increasing theclearance space; to provide such a fuel system wherein the system issubstantially closed preventing the entry 'of air to oxidize andotherwise contaminate the fuel and further, to prevent the formation offlammable fumes attendant such fuels; to provide such a systemparticularly adapted to the movement of jellied fuels employed in highspeed aircraft where the jellied fuels may be moved without the adverseeffect of channeling wherein the pressure medium seeks a channel throughthe fuel and often escapes through the fuel flow passage rather thandriving the fuel itself through said passage; to provide such a systemand reservoir which may be simply and inexpensively manufactured forutilization in various areas such as automobiles and aircraft to greatlyincrease the efficiency of moving flowable material and establishing asafe condition for the movement of various hazardous materials.

This invention contemplates a variable volume reservoir comprising afirst and second panel means with said panel means being disposed inspaced relation and interconnected by a wall means to form an enclosure.The invention further contemplates the inclusion of flexible means onsaid wall means to allow the relative movement of said panels inwardlyand outwardly of one another, said flexible means being formed of aflexible synthetic resin material, said material having a controlledrandomly orientated molecular structure or molecular alignment in aplurality of randomly directed planes capitalizing on the strengthobtained from molecular alignment without the disadvantage of creatingcleavage planes in the structure.

The invention further contemplates a method of forming said variablevolume reservoir comprising the steps of forming a parison having aninterior configuration like the exterior configuration of the finishedproduct, defining an interior chamber and an exterior, placing saidparison in a mold structure, heating said parison to a temperatureslightly below the melting point of the crystalline structure of saidparison and expanding the heated parison to the desired shape in acontrolled manner by regulating a slight pressure differential between apressure medium in the interior chamber and a medium about the exteriorof said parison.

The invention also contemplates that the variable volume reservoir maybe employed in systems for the movement of flowable material wherein thesystem includes means operatively connected to said reservoir to providea relative movement between the panels of said reservoir to therebyeffect a pressure on the flowable material in said reservoir. Thepressure applied to the reservoir itself and transmitted through thereservoir to the flowable material is employed to drive or move theflowable material within the material handling system.

Other objects and advantages of this invention will become apparent fromthe following description taken in connection with the accompanyingdrawings wherein are set forth by way of illustration and examplecertain embodiments of this invention.

FIG. 1 is a perspective view of a variable volume reservoir, containeror tank having a wall portion comprised of a circumferentially extendingbellows structure, said reservoir embodying the features of thisinvention.

FIG. 2 is a diagrammatic view of a system for moving or handlingfiowable material, particularly adapted to a system for supplyingcombustible fuel to the carburetor of an internal combustion engineshowing the variable volume tank as it would be utilized in the fuelsystem of a vehicle such as an automobile.

FIG. 3 is a side elevational view of a portion of the fuel handlingsystem shown in FIG. 2 illustrating the mounting and actuating means ofthe variable volume reservoir.

FIG. 4 is a vertical sectional view taken on line 44 of FIG. 2 showingthe variable volume tank and its actuating means.

FIG. 5 is a modified form of a collapsible tank and actuating meansparticularly adapted for utilization in an aircraft and capable of beingutilized by the movement of jellied fuels and shown as installed withinan aircraft wing structure.

FIG. 6 is a vertical sectional view through a mold structureillustrating the placement of a parison in a mold structure and showinga particular type of mold structure which may be employed to create avariable volume reservoir embodying the features of this invention.

FIG. 7 is a vertical sectional view through the mold structure of FIG. 6showing the parison in its initial stages of expansion wherein the upperand lower panels of the parison have been spread apart such that thelower panel is moved into contacting relation with the bottom surface ofthe mold structure.

FIG. 8 is a horizontal sectional view through the mold structure of FIG.6 illustrating a second phase of expansion of the parison wherein a pairof the side walls of the parison are expended into contacting relationwith a pair of correspondingly shaped side walls of the mold structure.

FIG. 9 is a vertical sectional view taken through the mold structureshown in FIG. 6 showing the parison in its final stage of expansionwherein the other pair of side walls of the parison are expandedoutwardly into contacting relation with the movable side walls of themold structure.

Referring to the drawings in more detail:

The reference numeral 1 generally designates a variable volume reservoiror tank having first and second spaced panels 2 and 4 respectively Withsaid panels 2 and 4 being joined together by means of acircumferentially extending side wall 6 to form an enclosure defining aninner chamber 8 for storage of a fiowable material. In the illustratedembodiment, the reservoir 1 is rectangular in plan view having arectangular upper panel 2, a rectangular lower panel 4 with a pluralityof side Walls 6 interconnecting the opposed spaced panels 2 and 4 toform the variable volume reservoir 1.

The circumferentially extending wall portion 6 includes flexible meansto allow the relative movement of the panels 2 and 4 inwardly andoutwardly of one another thereby varying the volume of reservoir andapplying pressure on the fiowable material within the reservoir 1 todrive or move the material through a particular system. In theillustrated embodiment, the flexible means is a portion of the side wall6 extending circumferentially about the reservoir 1 and comprised of acircumferentially extending bellows structure 10. The bellows structure10, as illustrated, is coextensive with the side wall 6 and extendscompletely about the reservoir 1 forming an accordian shaped structurewhich may be forced inwardly and outwardly to apply pressure on thematerial within said reservoir. The bellows structure 10 is comprised ofa plurality of corrugations or alternate grooves and ridges 12 and 14respectively extending from the upper panel 2 to the lower panel 4 in anintegrally formed structure.

The reservoir structure 1 has been so formed with a flexible plasticmaterial of a crystalline structure that the molecular structure of saidmaterial has been controlled in a randomly oriented manner such thatweaknesses along a single plane orientation or a cleavage plane in thestructure have not been created. Although molecular alignment has beencreated along random intersecting planes to provide additional strength.The random orientation of the molecular structure avoids the cleavageplanes normally attendant structures of this nature and the controlledexpansion generally regulates the molecular orientation in criticalareas of the reservoir 1 such that a reservoir is constructed havingunusual strength characteristics. The reservoir may be formed of variousplastic materials of a thermoplastic nature or a material tending toreturn to its original nature after heating and cooling and having thedesired characteristics of strength, flexibility and resiliency at awide temperature range and further, of such a. nature to be inert to thematerial contained within the reservoir 1. An example of such a materialis an olefin plastic material relatively impervious to gasoline.

Referring to FIG. 2, the reservoir structure 1 is illustrated in a fuelsystem designated by the reference numeral 16 in such a manner that thepressure is exerted on the collapsible reservoir 1 in order to movepanels 2 and 4 toward one another, thereby placing the fuel containedwithin the reservoir 1 under pressure and forcing said fuel through aconduit or passage 18 to a carburetor 20 associated with an internalcombustion engine 22. In this manner, the fuel movement or supply systemis free of internal pumps and valves which could cause leakage andcontamination of the fuel. The particular fuel system, as illustrated inFIG. 2, is of the type which could be adapted for utilization in variousvehicles such as automobiles and trucks wherein a hydraulic system 26 isemployed to exert the desired pressure on the reservoir structure 1. Thesystem illustrated in FIG. 2 is exemplary only as it is illustrative ofa single embodiment or means for applying pressures to the variablevolume reservoir 1 for providing sutficient pressure to move a flowablematerial contained within the reservoir 1 through a flow passage to adesired location.

In the illustrated emodiment, the hydraulic system 26 includes ahydraulic cylinder 28 operatively connected by a pair of hydraulic lines30 and 32 to a valve 34 which serves to control the flow of hydraulicfluid through lines 30 and 32 to the cylinder 28 to effect an actuationof the cylinder 28. The valve 34 is operatively connected in aconventional manner by lines 36 and 38 to a tank and pump for effectingthe flow of hydraulic fluid through the system 26. The valve 34 may becontrolled in various manners, but is illustrated herein as a solenoidvalve operatively connected by an electric circuit 40 to a set ofcontrols 42 which may be housed in the vehicle and employed foractuating or deactivating the cylinder 28 to apply or remove pressurefrom the flowable material within the reservoir 1. The pump in thehydraulic system 26 is operatively connected to the engine 22 and uponactuation of the engine 22, pumps fluid through lines 38 and 32 to thecylinder 28. A check valve is included in line 38 to maintain a linepressure on the piston of the cylinder after the deactivation of theengine 22. In order to fill the reservoir 1, the pressure exerted by thecylinder 28 is relieved by activation of valve 34 to line 32 to line 36and the tank of system 26.

Referring to FIGS. 2 and 3, the piston or driving rod 44 of thehydraulic cylinder 28 is swingably connected by a. suitable fitting 46to a cross bar 48, said cross bar 48, in turn, being swingably connectedto a pair of actuating linkage sets or systems 50 and 52 disposed onopposed sides of the reservoir structure 1. The linkage systems 50 and52 are employed for moving the opposed panels 2 and 4 of the reservoir 1together to exert pressure of the flowable material within the reservoir1.

Referring to FIGS. 3 and 4, the reservoir 1, as illustrated, has anupper or overlying plate 54 in contacting relation with the upper panel2 and a lower or underlying plate 56 in contacting relation with thelower panel 4, with the plate 56 being adapted for movement inwardly andoutwardly from the plate 54 with said plates 54 and 56 serving aspressure means for exerting pressure on the material within the variablevolume reservoir 1. In the illustrated embodiment, the plate 54 and 56are operatively connected for relative movement by the linkage systems50 and 52 with each of said systems being comprised of a connecting armor link 58 swingably mounted at an end portion of the cross bar 48. Thearm or link 58 is also swingably mounted to linkage means 60 for drawingthe plate 54 and 56 inwardly when a. force is exerted an the linkagemeans by the actuating arm or linkage 58. The linkage means 60 iscomprised of a horizontal member or link 62 which is swingably mountedto the linkage 58 and a pair of parallel links or members 64 and 66swingably mounted to each of the plates 54 and 56 such that thehorizontal displacement of the linkage 62 tends to pull the plates 54and 56 together to exert a pressure on the flowable material within thereservoir 1.

A swingably mounted diagonal bracing member 68 having opposed endportions 70 and 72 swingably connected to the plates 54 and 56respectively is utilized on opposed sides of the reservoir interiorly ofeach of the linkage systems 50 and 52 to maintain the plates in agenerally opposed relation and prevent the displacement horizontally ofthe lower plate 56 upon activation of the linkage systems 50 and 52.

The collapsible reservoir 1 contains a filling tube 80 integral with theupper panel 2 through which fluid or other flowable materials may beplaced within the reservoir 1 with a displacement cap 82 serving to sealthe tube 80 by threaded engagement therewith to prevent the entry of airthrough tube 80 and into the system 16. The cap 82, as illustrated,includes a protruding portion 84 extending downwardly within the tubularmember 80 to effect a displacement of the fluid or flowable materialcontained within the reservoir 1 in order to insure complete evacuationof air from the system by allowing the fluid or flowable material itselfto force the air outwardly upon engagement of the cap 82.

A gauge mechanism 86 is illustrated within the reservoir 1 to maintainan accurate reading of the fuel or other flowable material remainingwithin the reservoir 1 by monitoring the position of the lower plate 56in relation to the upper plate 54. In the illustrated embodiment, thegauge 86 is comprised of a rheostat 88 having an arm 90 for varying lineresistance extending outwardly therefrom, said rheostate 88 beingoperatively mounted to the upper panel 2 of the reservoir 1 and the arm90 extending downwardly toward the lower panel 4. The arm 90, asillustrated, has a roller 92 rotatably mounted to the lower portionthereof and disposed in rolling contacting relation to the lower panel 4of the reservoir 1 and designed to move laterally across the lower panel4 on activation of the hydraulic cylinder 28 moving the lower plate 56upwardly and forcing the flowable material from the reservoir 1. Therheostat 88 indicates the position or angular disposition of-the arm 90which may be reflected on a suitable reading means in a conventionalmanner. The conduit 18 includes a flexible end portion 93 which extendsthrough the upper plate 54 and the upper panel 2 of reservoir 1 to aposition at the lower portion of chamber 8 where the portion 93 issecured by a connector 94 to the lower panel 4 of reservoir 1. As thereservoir 1 is collapsed, the flexible end portion 93 folds up withinchamber 8 with its intake port 96 maintained at a relative position tothe lower panel 4 by the connector 94.

In operation, the reservoir 1 is filled with a fluid or other flowablematerial to the top of the filling tube and the cap 82 is replaced withthe protrusion 84 forcing out a certain amount of liquid or flowablematerial and any remaining air at the top of the tube 80. The hydrauliccylinder 28 is then activated by means of the controls 42 to maintain adesired predetermined pressure on the fuel in the reservoir 1 as thefuel is being depleted through utilization by the engine 22. Thehydraulic cylinder 28 maintains a constant pulling force on the crossbar 48 which, in turn, actuates the linkage systems 50 and 52 in such amanner as to pull the plates 54 and 56 inwardly of one another to exerta pressure on and collapse the reservoir 1 as the fuel therein isdepleted. The bellows structure 10 of the side wall 6 of the variablevolume reservoir 1 allows the reservoir 1 to collapse as the fuel isremoved therefrom.

The hydraulic pressure within the hydraulic system 26 can be maintainedby a pump operatively connected to the engine 22 with the check valve 39retaining the pressure when the pump is stopped and the vehicle is in aninoperative condition. In order to fill the tank or reservoir 1, it isnecessary to activate the controls 42 to open the line 30 to the line 38from the pump in order to drive the piston 44 outwardly of the cylinder28 to thereby spread the spacing between the plates 54 and 56 to allowthe collapsible reservoir 1 to be opened.

Referring to FIG. 5, a modified form of a variable volume reservoir ortank arrangement has been illustrated and is designated by the referencenumeral 100. The variable column reservoir arrangement 100 is adaptedfor utilization in the storage and movement of jellied fuels which arenormally employed in high speed aircraft. The variable volume reservoiror tank designated as 102 is formed in an identical manner to thatillustrated in FIG. 1 with the filling tube 80 omitted and including afilling port 103 and a discharge port 105. The variable volume reservoir102 has an upper panel 104 and a lower panel 106 disposed in contactingrelation to a pair of pressure means illustrated as plates 108 and 110with said plates 108 and 110 effecting a pressure on the fuel containedwithin the reservoir 102.

The panels 104 and 106 are operatively connected by means of acircumferentially extending side wall structure 112 having a flexiblemeans to allow the relative movement of the panels 104 and 106 forcompression of the fluid within the reservoir 102. The flexible means,as illustrated, is a circumferentially extending bellows structure 114which is integrally formed with the upper and lower panels 104 and 106respectively to form an enclosed chamber 116 for storage of a flowablematerial such as a jellied fuel.

The lower plate 110 is suitably mounted in a fixed position to a pair offrame members 118 as may be found in aircraft wing structures with theplate 108 movable relative to plate 110 and being actuated by aninflatable means 120 suitably mounted in a frame structure 122 such asan aircraft wing structure in overlying relation to the reservoir 102.

The inflatable means 120 is employed in a pressure exchanging manner inorder to effect a desired predetermined pressure on the fuel containedwithin the reservoir 102. As pressure is applied to the inflatable means120 through suitable means, the plate 108 is forced downwardly towardsplate 110, thereby effecting a pressure on the jellied fuel containedwithin the reservoir 102. As the pressure is being applied evenly acrossthe plate 104, the application of pressure to the jellied fuel isrelatively coextensive across the top or upper panel 104 of thereservoir 102. As the pressure medium is not being applied directly tothe jellied fuel, but rather through various pressure exchanging means,the effects of channeling whereby the pressure medium itself is lostthrough the fuel flow line is thereby avoided.

Referring to FIG. 6, a mold structure is illustrated and designated bythe numeral 130 which may be employed for forming collapsible reservoirsof the type described herein wherein the molecular structure of the tankitself is formed in a controlled random orientation, thereby avoidingthe weaknesses attendant cleavage planes which develop in the expandedenclosed structures of the prior art. The expansion of the preform orparison will tend to create an alignment of the molecular structure ofthe material along given planes and thereby create cleavage planes. Bythis method, alignment occurs in a random manner such as intersectingplanes of alignment such that cleavage planes are avoided and thestructure is strengthened in all directions with specific control" ofthe molecular alignment.

Initially, a parison or preform 132 is formed by conventional moldingprocesses such as rotational molding with said parison defining aninterior chamber 134 and an exterior surface 136 wherein the interiorconfiguration is like that of the exterior of the finished product. Theparison is formed of a material such as a thermoplastic synthetic resinwhich will remain in the condition of the original material afterheating and cooling of the material. The parison 132, as illustrated, ismolded with a circumferentially extending bellows structure 138interconnecting an upper panel 140 and a lower panel 142 such that theparison is a miniature unexpanded collapsible tank structure lacking thecontrolled molecular orientation or alignment of the finished product.The parison 132 includes an entry tube 144 which may later be employedas the filling tube 80 but is utilized during the molding or expandingprocess as an entry means for a heated pressure medium or fluid.

The mold structure 130, as illustrated, is comprised of an outer box orcase 146 having side walls 148, end Walls 150 and upper panel 152 and alower panel 154. Each of the side walls 148 contains a centrally locatedportion 156 formed in a corresponding manner to the desired bellowsshape of the finished collapsible tank and generally consisting of aplurality of corrugations or alternate ridges and grooves 155 and 157respectively extending across the height of the side walls 148.

The mold structure 130 also includes a pair of movable end walls 160'slidably retained within the mold structure 130 in spaced relation fromthe end walls 150 and movable by suitable means 162 operativelyconnected to the mold structure 130. The movable walls 160 each have aninner surface formed in a corresponding shape to the bellows portion ofthe finished reservoir 1 and being comprised of a plurality ofcorrugation or alternate ridges and grooves 161 and 163 respectively tothereby form the bellows structure. Each of the ridges 161 and 155 ofthe walls 160* and 148 has a cooling tube 164 operatively mounted inrelation thereto to effect a heat transfer from the parison as theparison is moved into contacting relation with the walls 160 and 148 tothicken the wall of the parison at the point of contact with the ridges161 and 155. The tubes 164 are each operatively connected to flexiblehoses 166 and 167 which extend outwardly of the mold structure to asuitable heat exchanging means. The walls 160 are each operativelymounted on a pair of arms 168 formed in an L-shaped manner, said arms168 being received through a pair of slots 170 defined in the side walls148 and suitably mounted to means for moving the walls inwardly andoutwardly from the center portion of the mold structure 130.

The pressure within the mold structure 130 is maintained through aconduit means 172 and gauges 173 which operatively connects saidstructure 130 to means for providing a pressure medium to the interiorof the mold structure 130 through an entry port 174. The movable walls160 of the mold structure 130 are provided with a plurality of minuteapertures which permit the maintenance and control of the desiredpressure within the mold structure throughout the entire inner interiorof said mold structure 130.

The parison, after being initially formed, is placed within the moldstructure with the entry tube 144 extending through an aperture 176defined in the upper panel 162 with the entry tube 144 being operativelyconnected to a means for providing a pressure medium to the interior 134of the parison 132. The pressure medium provided to the interior 134 ofthe parison 132 throughout the expansion of the parison 132 is heated toa temperature sufficiently high to maintain the temperature of theparison itself at a point slightly below the melting point of thecrystalline structure of the material forming said parison 132. A heatedpressure medium is also provided through the conduit 172 and ports 174into the interior of the mold structure to effect even heating of theparison 132, to allow control of the pressure differential between theinterior 134 of the parison and the interior 157 of the mold structurein such a manner as to accurately control the expansion of the parison132 and apply a uniform compressive force on the walls of the parisonduring its expansion. The employment of the pressure differential duringthe expansion prevents blow-through of the parison during expansion andallows a uniform wall formation diminishing the possibility ofestablishing areas of varying wall thickness.

As the heated pressure medium is provided to the interior 134 of theparison 132 to a degree in excess of pressure in the interior 157 of themold structure, the parison tends to expand and will initially expanddownwardly to a point where the bottom panel 142 of the parison 132contacts the bottom panel 154 of the mold structure. This initialexpansion is primarily due to the ease at which the parison 132 willexpand in this direction because of the bellows structure formed in theparison itself. At the time of initial expansion of the parison, themovable walls 160 are maintained inwardly toward the center portion ofthe mold structure 130 in order to prevent the outward expansion of theparison 132 toward the end walls of the mold structure. The expansion inthis direction is actually inhibited until full expansion has beenattained in the other two directions, downwardly and at right angles tothe direction of expansion toward the movable walls 160. The downwardexpansion of the parison occurs with the material at a temperatureslightly below the melting point of the crystalline structure, themolecules tend to align in chains in the direction of stretching of thematerial. The direction and amount of displacement will control thedegree of orientation obtained.

As shown in FIG. 7, the parison has expanded fully downward and thenreferring to FIG. 8, the parison is then expanded outwardly at rightangles to the direction of expansion toward the movable walls ortransversely of the mold structure 130 with the movable walls 160 stillmaintained inwardly toward the center portion of the mold structure 130thereby inhibiting the expansion of the parison outwardly toward the endwalls 150 of the mold structure 130 or longitudinally of the moldstructure 130. As the parison is initially expanded downwardly such thatthe upper panel 140 and lower panel 142 of the parison 132 are incontacting relation with the upper panel 148 and the lower panel 154 ofthe mold structure 130, the parison may then be expanded outwardly inlateral directions with the corrugation or bellows portion of the sidewalls of the parison 132 in aligned relation with the corrugation of thecentral portion 156 of the side walls 148 and the corrugation on themovable walls 160.

With the movable end walls 160 still positioned inwardly restricting theoutward movement of the parison in a direction longitudinally of themold structure 130, the parison is next expanded, as illustrated in FIG.8, out- 9 wardly into contacting relation with the central portion 156of the side walls 148 with the corrugations of the parison moving intomating engagement with the corrugations on the central portion 156 ofthe side walls 148. This subsequent stretching of the material at rightangles to the initial direction of stretch tends to diminish, to adegree, the previous orientation of the molecular structure in the sidewall area. The subsequent stretching tends to spread the initial chainsand form chains at generally right angles to the initial chains. Thischain formation, however, is not uniform in practice and results in arandom pattern of aligned molecules with intersecting chains such thatcleavage planes established by molecular orientation are reinforced byother alignments or chains thereby avoiding areas of weakness.

In order to provide the desired strength of the material in the bellowsstructure 10, a stretching of the material forming the pleats orcorrugations of the bellows is conducted. The corrugations on thecentral portion 156 of the side walls 148 have cooling tubes 164adjacent the ridge portions 155 to effect a heat transfer from thematerial as the material is moved into mating contacting relation withthe corrugations to stabilize the material by lowering its temperaturein this area. As expansion continues, the material in each pleatstretches outwardly to the outer apex of the pleat of the reservoirthereby tending to orient molecular chains from the apex of the valleytoward the apex of the ridge of the bellows 10 of the reservoir 1 toresist hoop stresses created in container structures of this nature. Theoverall effect is to create areas having randomly oriented molecularstructures which increase strength due to orientation without theeffects of weakness caused by cleavage planes between aligned molecularchains.

With the parison 132 expanded vertically and transversely to the moldstructure 130, the movable walls 160 are moved outwardly from the centerportion of the mold structure 130 and the parison 132 is expandedoutwardly into mating contacting relation with the corrugation on themovable end walls 160 to thereby complete the expansion of the parisoninto the final configuration of the collapsible reservoir 1. The coolingtubes 164 in the end walls 160 tend to stabilize the material of theforming reservoir as explained previously causing additional stretchingof the material from the valleys to the ridges of the pleats of thebellows structure 10 of the reservoir 1.

It should be noted that throughout the entire expansion operation, thetemperature of the parison is maintained at a point slightly below themelting point of the crystalline structure of said parison and adifferential pressure is maintained between the interior of the parisonand the exterior of said parison in order to effectively control therate of expansion of said parison 132 and maintain the walls of theparison 132 in compression. Although the movement of the parison onexpansion ofthe parison has been defined in steps, the overall processwill be conducted quite quickly and from a practical standpoint, theexpansion in the various directions will be almost simultaneous. Itshould also be noted that as the parison is expanded outwardly in alldirections, there are no forces exerted on the parison which would tendto cause or effect a molecular alignment along a single plane. Althoughalignment does occur throughout the enclosed structure, this alignmentis best described as random or along a plurality of intersecting planesin varying directions such that a single cleavage plane or a pluralityof cleavage planes are not created across the enclosed structure,thereby effecting weaknesses in certain directions. This is particularlyimportant in structures of this nature as various stresses will beapplied in a plurality of directions and Where cleavage planes exist inthis structure, failure at one time or another would be almostinevitable.

What I claim and desire to secure by Letters Patent is:

1. A variable volume reservoir in which the size changes to correspondto the quantity of material therein comprising:

(a) a first and second panel means, said panel means being disposed inspaced relation,

(b) wall means interconnecting said panels and being integrally formedtherewith to form a monolithic enclosure, said wall means including acircumferentially extending bellows portion of flexible material toallow the relative movement of said panels inwardly and outwardly of oneanother, said bellows portion being of a flexible plastic of acrystalline structure and having a controlled molecular orientation,provided by forming the wall means and allowing it to set and thenreheating same to a temperature near but below the melting point of thecrystals and expanding the structure to stretch the wall means in onedirection and then holding the panels while expanding the bellowsportion to stretch same in directions in different planes to the firstnamed stretch and then cooling the wall means to stabilize same in theexpanded position,

(c) said bellows portion having alternating ridges and valleys whereinsaid molecular orientation includes orientation directed generally alonglines extending from the valleys to the ridges and generally in thedirections of the valleys.

2. A system for movement of a fiowable material comprised of:

(a) a liquid and air-tight variable volume reservoir for flexiblematerial, said reservoir having first and second panel means and wallmeans, said wall means interconnecting said panel means and having acircumferentially extending bellows portion to form a container withflexible means on said wall means to permit the relative movement ofsaid first and second panels inwardly and outwardly of one another,

(b) said bellows portion of the wall means being formed of a flexibleplastic material of a crystalline structure with a plurality of orientedmolecular chains disposed in random pattern, provided by forming thebellows portion and allowing it to set and then reheating same to atemperature near but below the melting point of the crystals andexpanding the structure to stretch the bellows portion in one directionand then holding the panels while expanding the bellows portion tostretch same in directions indifferent planes to the first named stretchand then cooling the bellows portion to stabilize same in the expandedposition,

(c) said bellows portion having alternating ridges and valleys whereinsaid molecular orientation includes orientation directed generally alonglines extending from the valleys to the ridges and generally in thedirections of the valleys,

(d) a discharge connection communicating with the reservoir,

(e) means operatively connected to said reservoir to provide relativemovement between said panels to provide pressure on the fiowablematerial in said reservoir to effect flow of the material through saiddischarge connection.

References Cited UNITED STATES PATENTS 2,372,177 3/ 1945 Conner 222-1073,186,600 6/1965 Guignard 222107 3,197,082 7/1965 Palombo 2222l5 X2,432,025 12/1947 Lorenz 158-46 2,688,424 9/ 1954 Keiter 222-2152,696,247 12/1954 Hiltner 15 850.1 X 2,784,882 3/1957 Du Bois 222215(Other references on following page) 11 12 UNITED STATES PATENTS SAMUELF. COLEMAN, Primary Examiner 3,083,877 4/1963 Gash 222 107 US Cl.3,198,861 8/1965 Marvel 264-98 3,313,319 4/1967 Osborn et a1. 264-94X3,350,492 10/1967 Grootenboer 264-320 5

